1. Field of the Invention
The present invention is broadly concerned with a device which can be implanted in a body part (e.g., eye, tissue, artery) and methods of externally manipulating the device to adjust or alter the configuration of the body part. More specifically, the invention is directed towards the use of that device to adjust the curvature of the sclera of the eye so as to alter functional ocular structural relationships (e.g., such as to restore the accommodative ability of the eye), thus treating various eye conditions.
2. Description of the Prior Art
In order for the eye to clearly see an object at a distance of about twenty feet or greater, the object must be focused on the retina of the eye. When this occurs in the relaxed state of the eye, it is referred to as “emmetropia.” If the focal point is anterior to the retina, it is classified as “myopic.” On the other hand, if the focal point is behind the retina, it is classified as “hyperopic.”
Refractive correction is required to correct these focusing errors. This has typically been accomplished by the natural lens or by medical or surgical refractive devices. However, after the eye has been made to correctly focus on an object at a distance, it must then be capable of changing its refractive ability to see an object as it comes nearer the eye. This is accomplished physiologically through changes in the natural lens referred to as accommodation.
The ocular structures involved in accommodation include filaments inserted onto the lens equator and called zonules or zonular fibers. The zonules are connected to the ciliary body which is a muscle attached to the sclera that encircles and thus, in cooperation with the zonules, suspends the eye's lens. The actual mechanism by which these structures influence accommodation is still highly debated, but includes changes in lens shape and position with subsequent change in the overall refractive power of the eye.
Loss of accommodative ability, or presbyopia, occurs naturally with aging. It becomes noticeable at about forty years of age, and consistently worsens until about seventy years of age, at which time accommodation is effectively nonexistent. Theories concerning the causes of the loss of accommodative ability include increasing rigidity of the lens or its capsule, lens enlargement, laxity of the zonules, aging of the ciliary body, and combinations of the foregoing.
The usual way to correct this problem is to use bifocal lenses. However, some people dislike wearing glasses, particularly bifocals, for various reasons. One problem with bifocal lenses is that they present lines where the two portions of the lens are joined together. Furthermore, people must become accustomed to reading through one relatively small portion of the lens, while looking at distant objects through a different portion of the lens. Bifocal glasses also have the same disadvantages present in regular glasses. Such disadvantages include the fact that the glasses are breakable, become fogged when coming in from the cold, steam up in hot weather, and require frequent cleaning.
Other treatments have been attempted to correct presbyopia. For example, U.S. Pat. Nos. 5,928,129 and 5,802,923 each disclose the production of “bifocal-like” refractive correction through laser ablation of the inferior cornea.
Treatment methods have attempted to return the accommodative ability to a presbyope via expansion of the scleral radius in the vicinity of the ciliary body by a scleral expansion band (U.S. Pat. No. 5,489,299) or by a band which is adjustable at the time of placement (U.S. Pat. No. 5,354,331). Some methods have even shortened the zonules connecting the ciliary body to the lens by enzymes, heat, radiation, or surgical repositioning of the ciliary body.
Adjustable, ocular refractive devices for use in the cornea have been developed as well. Such adjustable devices include those which are adjustable at the time of placement. For example, U.S. Pat. No. 5,681,869 describes a poly(ethylene oxide) gel that is injected into the cornea in an amount sufficient to produce the required refractive correction. Additionally, U.S. Pat. No. 5,489,299 discloses a length-adjustable scleral expansion band for treatment of presbyopia, with the band length being measured and set at the time of placement. U.S. Pat. No. 5,919,228 discloses a corneal ring comprised of a memory metal that, upon insertion into the cornea, is caused to reach a temperature at which it assumes a prior impressed shape thus altering the shape of the cornea.
Other prior art devices include those which require further surgery to modify them if necessary after placement. For example, U.S. Pat. No. 5,855,604 discloses a hollow device placed into the cornea stroma. The device includes quantities of strands which may be removed at the time of placement, or which may be removed or added by surgery as needed after placement.
Each of the foregoing prior art techniques attempted thus far are lacking in that they only correct presbyopia at one particular stage of the disorder. Thus, as the condition worsens, the treatment would need to be repeated or otherwise enhanced. Or, in case of adjustable devices, additional surgery is needed to make the desired modifications. All of this poses undue risk to the eyes with each successive treatment.